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Quoted from this is evil evil

Hey man. You should know that IOBit software is largely incombatible with VAC’s system for some reason. I believe that Startmenu_hook/IOBit startmenu is the cause of your issue.

These guys had the same issue, and was using the same software: https://steamcommunity.com/discussions/forum/1/611696927932589956/

Removed all IOBit softwares and still the message appeared.

Quoted from bub

[…]

Removed all IOBit softwares and still the message appeared.

Hey, well I guess it’s time to isolate where the issue is then. Close all non-essential apps currently running, so only the necessary services/apps is running the background, to keep windows running. If the issue still occurs, I would say you need to run a full chkdsk to solve the issue, although it’s quite rare for that to be the cause of this.

If you are interested, I can also take a closer look at your setup, by providing me a HPSreport (For windows 8, download the one for windows server 2012 x64): http://update.external.hp.com/HPS/HPSreports/ – When running the .exe, it will collect a bundle of logs and put it in a .CAB file. Send that .CAB file to me, with a dropbox link or whatever you prefer.

I had this for maybe 6-8 weeks on and off. I read forums for a long time, i reinstalled windows and did everything steam support told me. No result.
I found the issue was iObit which was a overlay for the windows 8 start button. I uninstalled this and fixed. Make sure you uninstall all applications that run in the background all the time because that was my problem. My friend also has iObit installed and he never had the same problem as i did. Looks like this is completely random and is different to all computers.

Disabling Google Drive on startup worked for me and b0nes to stop this issue, if anyone needs any possible solutions other than ones they’ve tried.